Positively photosensitive resin composition

ABSTRACT

The positive-working radiation sensitive resin composition which has high sensitivity, high resolution and no residues in development and ability to form a pattern having a good profile. The positive-working radiation sensitive resin composition contains a mixed radiation sensitive novolak resin comprising the mixture of 1,2-naphthoquinonediazide-4-sulfonic acid ester of an alkali soluble novolak resin and 1,2-naphthoquinonediazide-5-sulfonic acid ester of an alkali soluble novolak resin, wherein the ratio by weight of the 1,2-naphthoquinonediazide-4-sulfonyl group and 1,2-naphthoquinonediazide-5-sulfonyl group ranges from 5:95 to 20:80.

TECHNICAL FIELD

This invention relates to a novel positive-working radiation sensitiveresin composition and, more particularly, to a positive-workingradiation sensitive resin composition containing a radiation sensitivenovolak resin, suited for manufacture of a semiconductor integratedcircuit, production of a display surface of a liquid crystal displaydevice in a LCD panel, manufacture of a circuit substrate for a thermalhead etc., and like use.

BACKGROUND ART

In the wide field of manufacturing a semiconductor integrated circuitsuch as a LSI, preparing a display surface of a liquid crystal displaydevice in a LCD panel, manufacturing a circuit substrate for a thermalhead etc., and like use, photolithography has so far been employed forforming microelements or conducting fine processing. In thephotolithography, a positive- or negative-working radiation sensitiveresin composition is used for forming a resist pattern. Of theseradiation sensitive resin compositions, those compositions containing analkali-soluble resin and a photosensitizer of quinonediazide compoundare most popularly used as the positive-working radiation sensitiveresin compositions. As such compositions, there are describedcompositions having different formulations as, for example, ‘novolakresin/quinonediazide compound’ in many documents such as JapaneseExamined Patent Publication Nos. S54-23570 (U.S. Pat. No. 3,666,473) andS56-30850 (U.S. Pat. No. 4,115,128), Japanese Unexamined PatentPublication Nos. S55-73045, S61-205933 and S62-51459, etc.

These compositions containing a novolak resin and a quinonediazidecompound have so far been studied from the viewpoint of both novolakresins and photosensitizers. From the viewpoint of a novolak resin,there have been developed novel resins. In addition, radiation sensitiveresin compositions having excellent properties have also been obtainedby improving properties of conventionally known resins. For example,there are disclosed techniques providing a radiation sensitive resincomposition having excellent properties by using a novolak resin with aparticular molecular weight distribution in Japanese Unexamined PatentPublication Nos. S60-140235 and H1-105243 and by using a novolak resinfrom which low-molecular-weight components of the resin has been removedby fractionation in Japanese Unexamined Patent Publication Nos.S60-97347 and S60-189739 and Japanese Patent Publication No.2590342.From the viewpoint of a photosensitizer, various attempts have been madeto develop novel quinonediazide compounds and novel quinonediazidesulfonates. Further, there have been proposed the improvement of thecharacteristics by a combination of a specific novolak resin and aquinone diazide sulfonate (e.g. Japanese Unexamined Patent PublicationH9-90622) or a combination of a specific dissolution promoter and aquinonediazide sulfonate of an alkali- soluble resin such as novolakresin (e.g. Japanese Unexamined Patent Publication No.H10-69077).Above-mentioned Japanese Unexamined Patent Publication Nos. H9-90622 andH10-69077 describe generally that quinonediazide sulfonates are formedby use of quinonediazide compounds having a sulfonic acid group at the4- or 5-position, and further that such sulfonates of quinonediazidecompounds having a sulfonic acid group at the 4- or 5-position are usedin combination, but there is no specific disclosure therein on thecombined use thereof such as an effect when used in combination thereof,a mixing ratio thereof, and Examples.

A number of positive-working radiation sensitive resin compositionscontaining quinonediazide compounds have been put into practice as aresult of various technical developments having so far been made, andthe aspect ratio of thickness of radiation sensitive resin coating toline width resolved has been improved to about 5:1 .

On the other hand, degree of integration of semiconductor integratedcircuits have been increased year by year and, in the manufacturethereof, processing of patterns with a line width of less thansub-micron order has become required. In the uses requiring suchsuper-fine processing, good pattern reproducibility is required as wellas high resolution and, from the standpoint of production cost, it isalso required to improve throughput (yield per unit time) uponproduction by meeting the high sensitization. However, conventionallyknown radiation sensitive resin compositions can not satisfy theserequirements at the same time, thus being a problem.

Under the circumstances with problems described above, an object of thepresent invention is to provide a positive-working radiation sensitiveresin composition which has high sensitivity and high resolution and canform a good pattern.

DISCLOSURE OF THE INVENTION

As a result of intensive investigation, the inventors have found that ina positive-working radiation sensitive resin composition comprising aradiation sensitive novolak resin consisting of esterified productsbetween an alkali-soluble novolak resin and naphthoquinonediazidecompounds, if said radiation sensitive novolak resin consists of twokinds of esterified products between an alkali-soluble novolak resin andnaphthoquinonediazide compounds different in the substitution positionof the sulfonic acid group and the mixing ratio of the substituent groupis in a specific range, the resulting positive-working radiationsensitive resin composition has high sensitivity, high resolution andability to form excellent patterns, which cannot be predicted from theprior art, thus having completed the present invention based on thefinding.

That is, the present invention relates to a positive-working radiationsensitive resin composition comprising partially esterified products(radiation sensitive novolak resin) between an alkali-soluble novolakresin and o-naphthoquinonediazide compounds, wherein said partiallyesterified products comprise 1,2-naphthoquinonediazide-4-sulfonic acidester and 1,2-naphthoquinonediazide-5-sulfonic acid ester, and the ratioby weight of 4-sulfonyl group and 5-sulfonyl group bound to saidpartially esterified products ranges from 5:95 to 20:80.

The present invention will now be described more specifically below.

An alkali-soluble novolak resin used as a starting material forpreparing the radiation sensitive novolak resin of the present inventionis a novolak-type phenol resin, and is manufactured by polycondensationbetween one of phenols or a mixture thereof and an aldehyde such asformalin. The polycondensation between a phenol and an aldehyde may beconducted by any conventionally known processes such as using oxalicacid as a catalyst.

The alkali-soluble novolak resin may be the one from which low-molecularcomponents were removed by suitable fractionation treatment such asre-precipitation. The removal of low-molecular components is conductedusually before the reaction between the alkali-soluble novolak resin andthe naphthoquinonediazide compounds. Alternatively, after the reactionof the alkali-soluble novolak resin and the naphthoquinonediazidecompounds, the reaction products may be treated in the same manner as inthe above-mentioned fractionation treatment of the novolak resin, sothat low-molecular components are removed from the reaction products,and the radiation sensitive novolak resin thus obtained is similar tothe one obtained from the novolak resin from which low-molecularcomponents were previously removed. However, from the viewpoint ofsafety and because of the possible inactivation of the radiationsensitive functional groups by heating at the time of fractionationtreatment, the fractionation treatment is conducted preferably beforethe reaction. If the novolak resin from which low-molecular componentswere removed by fractionation treatment is used, desired resolution maynot be achieved, so a predetermined dissolution inhibitor is preferablyblended with it.

In the present invention, there are preferably used an alkali-solublenovolak resin having a dissolution rate of 10 to 300 Å/sec, for a 2.38wt% aqueous solution of tetramethylammonium hydroxide measured accordingto the following “method of measuring dissolution rate of novolakresin”. If the dissolution rate of the alkali-soluble novolak resin isless than 10 Å/sec, such novolak resin can cause reduction insensitivity and remaining of indissoluble substances. In addition, it isdifficult to attain high resolution by use of such novolak resin. If thedissolution rate is more than 300 Å/sec, such novolak resin is notpreferable for the resist pattern by reason of much decrease in resistfilm thickness after development, and it is difficult to obtain resistpatterns with good reproducibility and a good profile of patterns by useof such novolak resin. (Method of measuring dissolution rate of novolakresin)

20 g of novolak resin is dissolved in 80 g of a mixed solvent of ethyllactate/n-butyl acetate (85/15), then filtered through a 0.5 μm Teflonfilter. The resulting resin solution is applied on a HMDS-treated 4-inchsilicon wafer using a spin coater, LARC ULTIMA-1000 made by LithotecJapan Co. and baked at 100° C. for 90 seconds on a hot plate to form a1μm-thick resist coating. Thickness of the coating is accuratelymeasured by means of an apparatus for measuring film thickness, LambdaAce made by Dainippon Screen Co., Ltd. Thereafter, the thus obtainedsilicon wafer is dipped in an alkaline developer solution, AZ® 300MIFDeveloper (a 2.38 wt % aqueous solution of tetramethylammoniumhydroxide) made by Clariant (Japan) K.K. at 23 ° C., and the timenecessary for the resin coating on the wafer to be completely dissolvedis measured. Dissolution rate of novolak resin is calculated from thecoating thickness and the dissolution time thus measured.

As the phenols to be used for manufacturing above-describedalkali-soluble novolak resins, there maybe illustrated cresols such aso-cresol, p-cresol and m-cresol; xylenols such as 3,5-xylenol,2,5-xylenol, 2,3-xylenol and 3,4-xylenol; trimethylphenols such as2,3,4-trimethylphenol, 2,3,5-trimethylphenol, 2,4,5-trimethylphenol and3,4,5-trimethylphenol; t-butylphenols such as 2-t-butylphenol,3-t-butylphenol and 4-t-butylphenol; methoxyphenols such as2-methoxyphenol, 3-methoxyphenol, 4-methoxyphenol, 2,3-dimethoxyphenol,2,5-dimethoxyphenol and 3,5-dimethoxyphenol; ethylphenols such as2-ethylphenol, 3-ethylphenol, 4-ethylphenol, 2,3-diethylphenol,3,5-diethylphenol, 2,3,5-triethylphenol and 3,4,5-triethylphenol;chlorophenols such as o-chlorophenol, m-chlorophenol, p-chlorophenol and2,3-dichlorophenol; resorcinols such as resorcinol, 2-methylresorcinol,4-methylresorcinol and 5-methylresorcinol; catechols such as5-methylcatechol; pyrogallols such as 5-methylpyrogallol; bisphenolssuch as bisphenol A, B, C, D, E or F; methylol-cresols such as2,6-dimethylol-p-cresol; naphthols such as α-naphthol, β-naphthol, etc.;and the like. These are used independently or as a mixture of two ormore thereof.

As the aldehydes, there may be used salicylaldehyde, paraformaldehyde,acetaldehyde, benzaldehyde, hydroxybenzaldehyde, chloroacetaldehyde,etc. as well as formalin. These are used independently or as a mixtureof two or more thereof.

On the other hand, 1,2-naphthoquinonediazide-4-sulfonic acid esters and1,2-naphthoquinonediazide-5-sulfonic acid esters constituting theradiation sensitive novolak resin of the present invention can beproduced in an arbitrary method known in the art. These are producedgenerally by dissolving, in a solvent,1,2-naphthoquinonediazide-4-sulfonyl halide and/or1,2-naphthoquinonediazide-5-sulfonyl halide along with thealkali-soluble novolak resin described above, followed by introducing abase such as triethylamine into the mixture. Because the reactionproceeds almost quantitatively, the amount of1,2-naphthoquinonediazide-4-sulfonyl halide or 1,2-naphthoquinonediazide-5-sulfonyl halide used in the reaction system can be regulatedto control the amount of the ester substituent groups.

Preferable examples of 1,2-naphthoquinonediazide-4-sulfonyl halidesincludes 1,2-naphthoquinonediazide-4-sulfonyl chloride and preferableexamples of 1,2-naphthoquinonediazide-5-sulfonyl halides include1,2-naphthoquinonediazide-5-sulfonyl chloride in the present invention.

As to reaction substitution ratio of the naphtoquinonediazide compoundto the alkali-soluble novolak resin, 3.5 to 25 mol % based on hydrogenatom of hydroxyl group of said novolak resin is preferred, with 4 to 15mol % being more preferred. If the reaction substitution ratio is lessthan 3.5 mol %, intended resolution is hardly attained, whereas if morethan 25 mol %, there results a positive pattern with developmentresidues and tends to form a worse pattern profile.

In the present invention, the 1,2-naphthoquinonediazide-4-sulfonyl groupand 1,2-naphthoquinonediazide-5-sulfonyl group described above arepreferably used as a mixture in a ratio by weight of from 5:95 to 20:80.If the ratio of the 1,2-naphthoquinone diazide-4-sulfonyl group is lessthan 5%, the resulting composition is poor in resolution, and duringdevelopment, scum is generated and the microgrooving characteristics aredeteriorated. On the other hand, if the ratio of the1,2-naphthoquinonediazide-4-sulfonyl group exceeds 20%, the shape ofpatterns is deteriorated. The mixture of1,2-naphthoquinonediazide-4-sulfonic acid ester and1,2-naphthoquinonediazide-5-sulfonic acid ester can be produced byseparately reacting each of their corresponding naphthoquinonediazidecompounds with the novolak resin to produce1,2-naphthoquinonediazide-4-sulfonic acid ester or1,2-naphthoquinonediazide-5-sulfonic acid ester followed by mixingthereof, or by allowing the naphthoquinonediazide compounds previouslymixed in a predetermined ratio to react with the novolak resin. However,it is preferable to use the former method wherein1,2-naphthoquinonediazide-4-sulfonic acid ester and1,2-naphthoquinonediazide-5-sulfonic acid ester are separately producedand then mixed.

The solvent for dissolving the radiation sensitive novolak resin of thepresent invention includes ethylene glycol monoalkyl ethers such asethylene glycol monomethyl ether and ethylene glycol monoethyl ether;ethylene glycol monoalkyl ether acetates such as ethylene glycolmonomethyl ether acetate and ethylene glycol monoethyl ether acetate;propylene glycol monoalkyl ethers such as propylene glycol monomethylether and propylene glycol monoethyl ether; propylene glycol monoalkylether acetates such as propylene glycol monomethyl ether acetate andpropylene glycol monoethyl ether acetate; lactates such as methyllactate and ethyl lactate; aromatic hydrocarbons such as tolueneandxylene; ketones such as methyl ethyl ketone, 2-heptanone andcyclohexanone; amides such as N,N-dimethylacetamide andN-methylpyrrolidone; and lactones such as γ-butyrolactone. Thesesolvents can be used independently or as a mixture of two or morethereof.

A photosensitizer containing a quinonediazide group other than1,2-naphthoquinonediazide-4-sulfonic acid ester and1,2-naphthoquinonediazide-5-sulfonic acid ester described above may beincorporated into the positive-working radiation sensitive resincomposition of the present invention as necessary. Thesephotosensitizers are obtained by allowing naphthoquinonediazidesulfonylhalide or benzoquinonediazidesulfonyl halide to react with alow-molecular or high-molecular compound having a functional groupcapable of condensation reaction with these sulfonyl halides. Thefunctional group that can be condensed with a sulfonyl halide includes ahydroxyl group, an amino group etc. Among these, a hydroxyl group isparticularly preferable. The compounds containing a hydroxyl groupinclude e.g. hydroquinone; resorcinol; hydroxybenzophenones such as2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone,2,4,6-trihydroxybenzophenone, 2,4,4′-trihydroxybenzophenone,2,3,4,4′-tetrahydroxybenzophenone, 2,2′,4,4′-tetrahydroxybenzophenoneand 2,2′,3,4,6′-pentahydroxybenzophenone; hydroxyphenylalkanes such asbis(2,4-dihydroxyphenyl)methane, bis(2,3,4-trihydroxyphenyl)methane andbis(2,4-dihydroxyphenyl)propane; and hydroxytriphenylmethanes such as4,4′,3″,4″-tetrahydroxy-3,5,3′,5′-tetramethylphenylmethane and4,4′,2″,3″,4″-pentahydroxy-3,5,3′,5′-tetramethyltriphenylmethane. Thesecan be used independently or as a combination of two or more thereof.

A low-molecular compound which has a phenolic hydroxyl group or groupsmay be incorporated as a dissolution inhibitor of a radiation sensitiveresin composition in the positive-working radiation sensitive resincomposition of the present invention. And there are illustrated, forexample, 4,4′,4″-methylidinetrisphenol,2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenol,4,4′-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bisphenol,4,4′,4″-ethylidinetrisphenol,4-[bis(4-hydroxyphenyl)methyl]-2-ethoxyphenol,4,4′-[(2-hydroxyphenyl)methylene]bis[2,3-dimethylphenol],4,4′-[(3-hydroxyphenyl)methylene]bis[2,6-dimethylphenol],4,4′-[(4-hydroxyphenyl)methylene]bis[2,6-dimethylphenol],2,2′-[(2-hydroxyphenyl)methylene]bis[3,5-dimethylphenol],2,2′-[(4-hydroxyphenyl)methylene]bis[3,5-dimethylphenol],4,4′-[(3,4-dihydroxyphenyl)methylene]bis[2,3,6-trimethylphenol],4-[bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)methyl]-1,2-benzenediol,4,6-bis[(3,5-dimethyl-4-hydroxyphenyl)methyl]-1,2,3-benzenetriol,4,4′-[(2-hydroxyphenyl)methylene]bis[3-methylphenol],4,4′,4″-(3-methyl-1-propanyl-3-ylidine)trisphenol,4,4′,4″,4′″-(1,4-phenylenedimethylidine)tetrakisphenol,2,4,6-tris[(3,5-dimethyl-4-hydroxyphenyl)methyl]-1,3-benzenediol,2,4,6-tris[(3,5-dimethyl-2-hydroxyphenyl)methyl]-1,3-benzenediol,4,4′-[1-[4-[1-[4-hydroxy-3,5-bis[(hydroxy-3-methylphenyl)methyl]phenyl]-1-methylethyl]phenyl]ethylidene]bis[2,6-bis(hydroxy-3-methylphenyl)methyl]phenol,and the like. If these low-molecular compounds having phenolic hydroxylgroup or groups are used, they are used in an amount of usually 2 to 20parts by weight relative to 100 parts by weight of the radiationsensitive novolak resin.

Dyestuffs, adhesive aids, surfactants etc. conventionally used asadditives of the positive-working radiation sensitive resin compositionmay be incorporated as necessary into the positive-working radiationsensitive resin composition of the present invention. The dyestuffsinclude e.g. Methyl Violet, Crystal Violet, Malachite Green etc.; theadhesive aids include e.g. alkyl imidazoline, butyric acid, alkyl acid,polyhydroxystyrene, polyvinylmethyl ether, t-butyl novolak, epoxysilane, epoxy polymer, silane etc.; and the surfactants include e.g.nonionic surfactants such as polyglycols and derivatives thereof such aspolypropylene glycol, polyoxyethylene lauryl ether etc.,fluorine-containing surfactants such as Fluorad (trade name;manufactured by Sumitomo 3M Ltd.), Megafac (trade name; manufactured byDainippon Ink & Chemicals, Inc.), Sulflon (trade name; manufactured byAsahi Glass Co., Ltd.) or organosiloxane surfactants such as KP341(trade name; Shin-Etsu Chemical Co., Ltd.).

Furthermore, the positive-working radiation sensitive resin compositionof the present invention may be used in combination with an inorganicanti-reflective coating of TiN, SiN, SiON or the like or an organicanti-reflective coating of AZ® BARLi, AZ® BARLi II (manufactured byClariant (Japan) K.K.).

The positive-working radiation sensitive resin composition of thepresent invention is applied on a substrate such as a silicon waferhaving an anti-reflective coating thereon, by spin coating or the like,and the substrate on which the radiation sensitive resin composition hasbeen coated is subjected to baking to form a radiation sensitive resincoating. The substrate having thereon the radiation sensitive resincoating is exposed with radiation such as ultraviolet rays, deepultraviolet rays, X-rays or electron beams and is developed with analkaline developing solution to form a resist pattern with highresolution and good pattern profile.

EXAMPLES

The present invention will now be described specifically by reference toExamples which, however, are not to be construed to limit the presentinvention in any way.

Synthesis Example 1

Synthesis of Novolak Resin A

80 g of m-cresol, 120 g of p-cresol, 112 g of a 37 % formalin aqueoussolution and 0.32 g of oxalic acid were charged in a 1-liter separableflask equipped with a stirrer, a condenser and a thermometer, and heatedto 100° C. under stirring, followed by reacting for 16 hours.Thereafter, the temperature was raised to 200° C., and the pressure wasgradually reduced to 1 mmHg to thereby remove water, unreacted cresolmonomer, formaldehyde, oxalic acid, etc. Then, molten novolak resin wastaken out of the flask and cooled to room temperature to solidify andrecover the reaction product. Molecular weight of thus obtained novolakresin A was measured under the conditions described below according togel permeation chromatography (GPC). Weight average molecular weight ofthe novolak resin A as determined using polystyrene standards was 6,800. The dissolution rate of the novolak resin A for a 2.38 wt % aqueoussolution of tetramethylammonium hydroxide measured by the aforementioned“method of measuring dissolution rate of novolak resin” was 199 Å/sec.

Measurement of the Novolak Resin According to GPC

Columns:GPC columns made by Showa Denko K.K. (one column of KF-804, twocolumns of KF-802 and one column of KF-801)

Flow rate:1.0 ml/min

Mobile phase: tetrahydrofuran (THF) for liquid chromatography grade

Column temperature: 40° C.

Synthesis Example 2

Synthesis of Radiation Sensitive Novolak Resin A

60 g of the novolak resin A, 6.71 g of1,2-naphthoquinonediazide-4-sulfonyl chloride and 250 g of acetone werecharged in a 1-liter, three-necked separable flask equipped with astirrer, a dropping funnel and a thermometer, and stirred to completelydissolve. Then, the flask was dipped in an ice-bath till the temperatureof the contents in the flask decreased to 15° C. and the ice-bath wasremoved. Then, 3.83 ml of triethylamine was dissolved in 25 ml ofacetone and charged in the dropping funnel, then dropwise added to themixture in the flask over one hour. After stirring for further 10minutes, the contents inside the flask were filtered to removetriethylamine hydrochloride. Thereafter, the filtrate was graduallyadded dropwise to 4,000 ml of 0.1 N hydrochloric acid aqueous solutionwith starring to obtain a precipitate. This precipitate was washed withwater, filtered out, and dried at 40° C. for 48 hours under reducedpressure to obtain radiation sensitive novolak resin A.

Synthesis Example 3

Synthesis of Radiation Sensitive Novolak Resin B

In the same manner as in Synthesis Example 2 except for changing1,2-naphthoquinonediazide-4-sulfonyl chloride to1,2-naphthoquinonediazide-5-sulfonyl chloride, there was obtained aradiation sensitive novolak resin B.

Examples 1 to 5, Comparative Example 1 to 5

50 g of a mixed radiation sensitive novolak resin, in which radiationsensitive novolak resins A and B prepared in the Synthesis Example 2 or3 were respectively contained in the proportions shown in Table 1 belowand 0.05 g of a surfactant of Megafac R-08 (manufactured by DainipponInk & Chemicals, Inc.) were dissolved in 80 g of a mixed solvent ofethyl lactate/n-butyl acetate (85/15). These solutions were filteredthrough a 0.5 μmTeflon filter and obtained positive-working radiationsensitive resin compositions of Examples 1 to 5 and Comparative Examples1 to 5.

Thus obtained positive-working radiation sensitive resin compositions ofExamples 1 to 5 and Comparative Examples 1 to 5 were respectivelyapplied, exposed and developed to form positive resist patternsaccording to the method in the following “evaluation ofradiation-sensitive resin composition” and then evaluated with respectto sensitivity, resolution, pattern form, scumming, and microgroovingcharacteristics according to the following evaluation. Results thusobtained are tabulated in Table 1.

(Evaluation of Radiation Sensitive Resin)

A positive-working radiation sensitive resin composition is applied on aHMDS-treated 4-inch silicon wafer using a spin coater, LARC ULTIMA-1000made by Lithotec Japan Co. and pre-baked at 110° C. for 120 seconds on ahot plate to form an about 6 μm-thick resist coating. The thickness ofthe radiation sensitive resin coating is measured by means of a filmthickness-measuring apparatus, Lambda Ace made by Dainippon Screen Co.,Ltd. The silicon wafer is exposed using a g-line exposure apparatushaving an exposure wavelength of 436 nm (DSW6400 made by GCA Co., Ltd.,NA=0.42) or i-line exposure apparatus having an exposure wavelength of365 nm (LD-5015iCW made by Hitachi Ltd., NA=0.50) with stepwise changingthe exposure amount. After the exposure, the wafer is developed bydipping in an alkaline developer (AZ® 300MIF developer, a 2.38 wt-%aqueous solution of tetramethylammonium hydroxide) made by Clariant(Japan) K.K. at 23° C. for 5 minutes to obtain a positive resistpattern.

(1) Sensitivity

‘Sensitivity’ was assessed as an amount of exposure energy capable offorming isolated 1.2 μm space as designed by a reticle pattern whenusing a g-line exposure apparatus and an amount of exposure energycapable of forming isolated 1.0 μm space as designed by a reticlepattern when using an i-line exposure apparatus.

(2) Resolution

Minimum pattern dimension resolved by the exposure amount described in(1) above.

(3) Form of pattern

Cross-sectional form of the isolated space of resist patterns on thewafer is observed under a scanning electron microscope (SEM), and formof pattern is rated according to the following criteria:

∘: No reduction of coating thickness observed, and increase of patterndimension at a height of ⅔ of the resist coating thickness from thesubstrate being less than +10% based on the bottom dimension of theisolated space;

Δ: No reduction of coating thickness observed, and increase of thepattern dimension being +10% to less than +15%;

X: Increase of the pattern dimension being +15% or more, or somereduction of coating thickness observed.

(4) Scuming (development residue)

Pattern form of space patterns isolated at a critical resolution isobserved under a scanning electron microscope (SEM), and scumming israted according to the following criteria:

∘: No development residues observed on the substrate and at theinterface with resist pattern.

Δ: Slight development residues observed.

X: Considerable development residues observed.

(5) Microgrooving

Pattern form of space patterns isolated at the critical resolution isobserved under a scanning electron microscope (SEM), and presence ofmicrogrooving is rated according to the following criteria:

∘: No under-cut of pattern observed at the interface between resistpattern and the substrate.

Δ: Slight under-cut of pattern observed.

X: Considerable under-cut of pattern observed.

TABLE 1 Radiation sensitive novolak resin Sensitivity Resolution Amountof Amount of (mJ/cm²) (μm) Pattern profile Scumming Microgrooving Aadded B added g-line i-line g-line i-line g-line i-line g/i-lineg/i-line Example 1 5.0 95.0 570 780 0.90 0.70 ◯ ◯ ◯ ◯ Example 2 7.5 92.5570 780 0.90 0.70 ◯ ◯ ◯ ◯ Example 3 10.0 90.0 580 755 0.90 0.70 ◯ ◯ ◯ ◯Example 4 15.0 85.0 610 750 0.90 0.75 ◯ ◯ ◯ ◯ Example 5 20.0 80.0 640745 0.90 0.75 ◯ ◯ ◯ ◯ Comparative — 100.0 560 770 1.00 0.80 ◯ ◯ X XExample 1 Comparative 2.5 97.5 565 770 0.90 0.75 ◯ ◯ Δ ◯ Example 2Comparative 25.0 75.0 670 740 0.95 0.80 ◯ Δ ◯ ◯ Example 3 Comparative30.0 70.0 700 730 0.95 0.90 Δ Δ ◯ ◯ Example 4 Comparative 50.0 50.0 820710 0.95 1.00 Δ Δ ◯ Δ Example 5

EFFECT OF THE INVENTION

As has been described in detail hereinbefore, high sensitivity, highresolution, no residues in development and ability to form excellentpatterns, which cannot be predicted from the prior art can be attainedby the positive-working radiation sensitive resin composition of thepresent invention using two kinds of specificnaphtoquinonediazide-sulfonic acid esters in a specific proportion. Andthe positive-working radiation sensitive resin composition of thepresent invention is extremely useful as a resist material formanufacturing semiconductor integrated circuits, preparing a displaysurface of liquid crystal display panel, manufacturing a circuitsubstrate for thermal head etc., in these fields where being expectedthat miniaturization will proceed more and more hereafter.

INDUSTRIAL UTILITY

The positive-working radiation sensitive resin composition of thepresent invention can be used as a resist material in manufacturingsemiconductor integrated circuits, preparing of display surface of LCDpanel, manufacturing of circuit substrate of thermal heads and the like.

What is claimed is:
 1. A positive-working radiation sensitive resincomposition comprising a partially esterified product of analkali-soluble novolak resin with o-naphthoquinonediazide compounds,wherein said partially esterified product comprises1,2-naphthoquinonediazide-4-sulfonic acid ester and1,2-naphthoquinonediazide-5-sulfonic acid ester, and the ratio by weightof the 4-sulfonyl group and 5-sulfonyl group bound to said partiallyesterified product ranges from 5:95 to 20:80.
 2. The positive-workingradiation sensitive resin composition according to claim 1 wherein thedissolution rate of the alkali-soluble novolak resin is in the range of10 to 300 Å/sec. in 2.38 wt % aqueous solution of tetramethylammoniumhydroxide.